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| United States Patent |
6,148,859
|
|
Fuller
|
November 21, 2000
|
Hydraulic control valve assemblies for hydraulic braking systems
Abstract
A solenoid-controlled valve assembly comprises a solenoid (1) for
controlling operation of a spool valve (2), and the solenoid is contained
within a solenoid body (3). The spool valve comprises a spool (40) working
in a bore (41, 42) in a spool housing (12), and the housing is, in turn,
sealingly received in a spool body (10). The housing (12) may be of
differential area and may be sealingly received in a complementary stepped
bore (11) in the spool body, with the housing arranged in such a manner
that when subjected to equal pressures over different area a resultant
force tends to urge the housing in a given direction. In a modification
the housing (12) may be resiliently biased away from the spool body (10)
and relatively towards the solenoid (1) by a resilient member such as an
annular ring (70) of elastomeric material, or a spring washer (71).
| Inventors:
|
Fuller; Robert Gregory (Coventry, GB)
|
| Assignee:
|
Lucas Industries, plc (Solihull, GB)
|
| Appl. No.:
|
201561 |
| Filed:
|
November 30, 1998 |
| Current U.S. Class: |
137/625.65; 137/596.17; 303/119.2 |
| Intern'l Class: |
F16R 031/02; B60T 008/36 |
| Field of Search: |
137/625.65,596.17
303/119.1,119.2
|
References Cited
U.S. Patent Documents
| 3880476 | Apr., 1975 | Belart et al. | 303/119.
|
| 4422475 | Dec., 1983 | Aspinwall | 137/596.
|
| 5076538 | Dec., 1991 | Mohr et al.
| |
| 5163474 | Nov., 1992 | Rizk | 137/596.
|
| 5221129 | Jun., 1993 | Takasaki | 303/119.
|
| 5306076 | Apr., 1994 | Tyler | 137/596.
|
| 5445447 | Aug., 1995 | Farr et al. | 303/119.
|
| 5678902 | Oct., 1997 | Farr et al. | 303/119.
|
| Foreign Patent Documents |
| 195 37 349 | Apr., 1996 | DE.
| |
Primary Examiner: Rivell; John
Attorney, Agent or Firm: MacMillan Sobanski & Todd, LLC
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of International Application No.
PCT/GB97/01307, filed May 14, 1997, which claims priority from British
Patent Application No. 9611534.0, filed Jun. 1, 1996.
Claims
What is claimed is:
1. A hydraulic control valve assembly comprising:
a spool valve, wherein said spool valve comprises a spool body, a spool
housing having a bore, a spool working in said bore, and said housing in
turn being sealingly received in said spool body, wherein biasing means
are incorporated for urging said spool housing in a given direction,
wherein said biasing means are defined by constructing said spool housing
of differential area, and said spool body being provided with a
complementary stepped bore in which said housing is received, said housing
being arranged in such a manner that when subjected to equal pressures
over different areas, a resultant force tends to urge housing in the said
given direction.
2. A valve assembly according to claim 1, and having a datum face, wherein
a sealing diameter of said housing is of a diameter smaller than a sealing
diameter is of the remainder of said housing, whereby said spool housing
is subjected to a resultant force acting to urge said housing in a
direction towards said datum face as a result of high-pressure fluid
acting over said two different areas, and being effective to clamp said
housing with respect to said datum face.
3. A hydraulic control valve assembly comprising:
a spool valve, wherein said spool valve comprises a spool body, a spool
housing having a bore, a spool working in said bore, and said housing in
turn being sealingly received in said spool body, wherein biasing means
are incorporated for urging said spool housing in a given direction,
wherein said biasing means comprise a resilient device acting between said
spool body and said spool housing to bias said spool housing relatively
away from said spool body.
4. A valve assembly according to claim 3, wherein said resilient device
comprises an annular ring of elastomeric material.
5. A valve assembly according to claim 3, wherein said resilient device
comprises a spring washer.
6. A valve assembly according in claim 3, wherein said spool housing has an
inner end, and said spool body has a shoulder at a complementary inner
end, and wherein said resilient device is positioned between said inner
end of said spool housing and said shoulder on said spool body.
7. A hydraulic control valve assembly comprising:
a spool valve, wherein said spool valve comprises a spool body, a spool
housing having a bore, a spool working in said bore, and said housing in
turn being sealingly received in said spool body, wherein biasing means
are incorporated for urging said spool housing in a given direction,
incorporating a solenoid body, and a solenoid contained within said
solenoid body for controlling operation of said spool valve, said solenoid
having an armature, wherein said spool is of differential outline and said
bore in which said spool works is of complementary stepped outline so
chosen that, in operation, a feed back force is transmitted to said
armature of said solenoid.
8. A hydraulic control valve assembly comprising:
a spool valve, wherein said spool valve comprises a spool body, a spool
housing having a bore, a spool working in said bore, and said housing in
turn being sealingly received in said spool body, wherein biasing means
are incorporated for urging said spool housing in a given direction
wherein said spool and said housing are each respectively in the form of
first and second spool members, which co-operate at adjacent ends, and
first and second housing components, also which co-operate at adjacent
ends.
9. A valve assembly according to claim 8, wherein one spool member works in
a complementary bore in a corresponding one of said housing components,
and the other spool member works in a complementary bore in the other one
of said housing components.
10. A valve assembly according to claim 8, wherein one of said housing
components is of external differential outline and the diameter of a
portion which is of greater area corresponds with the external diameter of
said other housing component.
Description
BACKGROUND OF THE INVENTION
This invention relates to hydraulic control valve assemblies for vehicle
hydraulic braking systems, for example for braking systems of the
electro-hydraulic type.
Known hydraulic control valve assemblies, for example solenoid-control
valve assemblies for use in electro-hydraulic vehicle braking systems,
typically incorporate a spool working in a bore in which movement of the
spool acts to connect and disconnect passages for providing communication
between an hydraulic power source, brake, and an hydraulic master
cylinder. Such spools and the respective housings provided with the bores
in which the spools work have to be manufactured to high accuracy and very
small tolerances in order to ensure that any leakage around the spool or
across edges of the spool is reduced to an absolute minimum. Since the
clearance between the spool and the housing is very small, care must be
taken to avoid or eliminate any imperfections or distortions in the bore
which could cause the spool to stick or lock at least during attempted
movement within the housing. Since the spool housing has to be secured
within a body in a fluid tight chamber, it is usual to clamp a housing by
using a plate, or the body of the solenoid, up against the bottom of the
bore within the body in which the housing is received. The application of
a clamp load can, if sufficiently large, cause distortion of the housing
bore to a degree sufficient to prevent the spool, itself, from moving
freely within the bore in the housing. As the effective length of the
housing, and the depth of the bore within the body and in which the
housing is received, can vary from one assembly to another so can the
clamp load since the extent of the clamp load depends upon the
interference presented by the housing with respect to the clamp plate or
the body.
SUMMARY OF THE INVENTION
According to one aspect of our invention in an hydraulic control valve
assembly comprising a spool valve, the spool valve comprises a spool
working in a bore in a spool housing, and the housing is, in turn,
sealingly received in a spool body, biasing means being incorporated for
urging the spool housing in a given direction.
This has the effect of preventing distortion of the spool housing due to
excessive loads, with consequent distortion of its bore, whereby to
eliminate the possibility of the spool sticking within the bore in which
it works.
The biasing means may be defined by constructing the spool housing of
differential area, with the housing received in a complementary stepped
bore in the spool body, and the housing being arranged in such a manner
that when subjected to equal pressures over different areas a resultant
force tends to urge the housing in the said given direction.
When operation of the spool valve is controlled by a solenoid contained
within a solenoid body, a sealing diameter of the housing remote from the
solenoid body may be of a diameter smaller than a sealing diameter of the
remainder of the housing. Thus the spool housing will be subjected to
resultant force acting to urge in a direction towards the solenoid body as
a result of high-pressure fluid, for example in an hydraulic accumulator,
acting over the two areas and being effective to clamp it with respect to
the solenoid body which, itself, is rigid with the spool body.
Since the spool housing is now clamped against the bodies by a resultant
force dependent upon the pressure stored in the accumulator, it is
possible to guarantee a suitable clamp load to hold the spool housing
against a datum face presented by the solenoid body without over clamping
the spool housing, whereby to avoid distortion of the bore in which the
spool works.
In another construction the biasing means comprises a resilient device
acting between the spool body and the spool housing to bias the spool
housing relatively away from the spool body.
The resilient device is resiliently deformed as the solenoid is secured in
position with the spool housing urged inwardly into the spool bore.
Thus the spool housing can be held against a datum face presented by the
spool body by compliant biasing and without the use of fluid pressure.
This avoids over clamping the spool housing, whereby to avoid distortion
of the bore in which the spool works.
The resilient device may comprise an annular ring of elastomeric material,
suitably an "O" ring, or it may comprise a Belleville or other spring
washer.
The resilient device may be positioned between the inner end of the spool
housing and a shoulder or step at the complementary or inner end of the
spool body.
Preferably the spool is of differential outline and the bore in which it
works is of complementary stepped outline so chosen that, in operation, a
feed back force is transmitted to an armature of the solenoid to
counteract the force developed by the solenoid due to fluctuations in
pressure applied to the brakes, and which acts on opposite ends of the
spool.
The spool and the spool housing may each comprise a single component.
However such components are difficult to manufacture in view of the close
tolerances required, both with regard to the external dimensions of the
housing, a stepped bore in the housing, and the external diameters of the
spool.
It is preferred, therefore, and according to another aspect of our
invention to construct the spool and the spool housing each in the form of
first and second spool members which co-operate at adjacent ends, and
first and second housing components, which also co-operate at adjacent
ends.
Conveniently one spool member works in a complementary bore in a
corresponding housing component, and the other spool member works in a
complementary bore in the other housing component.
One of the housing components is of external differential outline of which
the diameter of the portion of greater area corresponds with the external
diameter of the other housing component.
We therefore produce two relatively simple, as well as relatively short,
spool members which can easily be manufactured and which when assembled
eliminate the problems associated with concentricity between the
respective diameters at the ends of the spool valve. The spool members
themselves still operate as a single spool with the pressure acting across
the outer ends of the spool members providing a necessary holding force to
maintain the two spool members in close co-operation.
Some embodiment of our invention are illustrated in the accompanying
drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal cross-section through a solenoid-controlled valve
assembly with brakes in an off or released position:
FIG. 2 shows the relative positions when the valve assembly is operated to
apply the brakes; and
FIG. 3 shows the valve assembly in a position in which the brakes are held
`on`;
FIG. 4 is a view of the inner end of the spool body showing a modification:
and
FIG. 5 is a view similar to FIG. 4 showing a different construction of
biasing means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The solenoid-controlled valve assembly illustrated in the drawings
comprises a solenoid 1 for controlling operation of a spool valve 2.
The solenoid 1 comprises a solenoid body 3 in which an armature 4 is
axially displaceable in response to energisation of a coil 5 surrounding
the armature 4. The coil 5 is enclosed within a casing 6.
The spool valve 2 comprises a spool body 10 provided with a stepped,
longitudinally extending, bore 11 in which a housing 12 is received for
limited movement in an axial direction. The bore 11 is counter bored at
13, at its end of greater diameter and is internally screw threaded to
receive an externally screw threaded extension 14 at the forward end of
the solenoid body 3. A sealing ring 15 is clamped between the counter bore
13 and the extension 14.
The bore 11 has a first bore portion 20 of smaller diameter and of area `X`
at the end remote from the solenoid and which is disposed on one side of a
first radial port 21 for connection to an hydraulic accumulator (not
shown). The port 21 leads into a second bore portion 22 of greater
diameter and into which second radial port 23 for connection to a tank for
hydraulic fluid (not shown) also leads and which terminates in the counter
bore 13. The second bore portion 22 is of area `Y`. At the end remote from
the first bore portion 20, the bore 11 leads into a chamber 24, in turn
terminating in an axial passage 25 of the jurist area for connection to
brakes (not shown). An internal passage 26 connects the chamber 24 to the
counter bore 13.
The housing 12 comprises first and second housing components 30 and 31
which abut at adjacent ends with radial passages 32 defined between the
housing components 30, 31 communicating with the second radial port 23.
The first housing component 30 is of stepped outline and carries spaced
seals 33, 34 which engage sealingly with a respective bore portions 20 and
22. The second housing component 31 carries a seal 35 for sealing
engagement with the bore portion 22.
A spool 40 works in co-axial bores 41 and 42 in the housing components 30
and 31, of which the bore 41 is of greater diameter than the bore 42.
Specifically the bore 41 is of area `A`, and the bore 42 is of area `B`.
The spool 40 comprises a first spool member 43, and the second spool
member 44. The spool members 43 and 44 are in abutment at adjacent ends.
The spool member 43 has spaced lands 45, 46 which work in portions of the
bore 41 on opposite sides of a radial port 47 in the housing component 30,
with passages 48 in the spool member 43 leading from a space between the
lands 45, 46 into the chamber 24. The spool member 44 works in the bore
42. Reduced diameter portions 50, 51 at the adjacent ends of the spool
members 43 and 44 are in abutment, and a shoulder 52 and a step in
diameter between the spool diameter of the spool member 44 and the reduced
diameter portion 51 co-operates with a radial port 53 in communication
with the passage 26.
When the brakes are in an off or released position the components of the
solenoid valve assembly are in the relative positions shown in FIG. 1 of
the drawings, with the spool 40 urged towards the solenoid body 3 by means
of a spring 54 acting between the spool 40 and an abutment 55.
As illustrated the end of the first housing component 30 remote from the
component 31 is spaced from a shoulder 60 between that end of the bore 11
and the chamber 34, by a small clearance.
The accumulator is isolated from the brakes by the land 45 closing the
passage 47 and the brakes are in free communication with the reservoir
through the passage 26, the port 53 and the radial port 53.
When the solenoid 1 is energised to apply the brakes, the armature 4 urges
the spool 40 relatively towards the opposite end of the body 10, initially
to cause the shoulder 52 to close the radial port 53 leading to the
reservoir, and subsequently to cause the land 45 to open the port 47 so
that fluid from the accumulator is then supplied to the brakes through the
passage 48 in the spool 40.
Due to the provision of the internal passage 26 in the body 10 the outer
ends of both spool members 43 and 44 are subjected to equal pressure from
the hydraulic accumulator.
Equal pressures are therefore applied from the hydraulic accumulator over
the different areas X and Y of the housing 12, and the different areas A
and B of the spool 40. This defines biasing means acting in such a manner
that the housing 12 is subjected to a resultant force which urges it
against the solenoid body 3. The body 3 defines a datum face, and the
spool 40 is urged in a corresponding direction to apply a feedback force
to the armature 4 in order to counteract the force developed by the
solenoid 1 due to fluctuations in pressure applied to the brakes. The
relative positions of the components with the brakes applied are
illustrated in FIG. 2 of the accompanying drawings.
Should it be desired to hold the brakes `on` at a controlled pressure, the
energising current applied to the coil 5 is reduced, or pulsed. This
permits the armature 4 and the spool 40 to retract so that the land 45
closes the passage 47, but not through a distance sufficient for the
shoulder 52 to uncover the port 53.
When the brakes are released by cutting off the energising current to the
coil 5, the solenoid-controlled valve assembly is restored to the initial
position illustrated in FIG. 1 with the brakes isolated from the hydraulic
accumulator, and with braking pressure relieved to the reservoir through
the internal passage 26 and the radial port 23.
In the modified construction illustrated in FIG. 4 of the accompanying
drawings, the biasing means comprise an "O" ring in the form of an annular
ring 70 of resilient elastomeric material which is disposed between the
inner end of the spool housing 12 and the shoulder 60.
The material of the ring 70 is resiliently deformed as the solenoid is
screwed in position with the spool housing 12 urged inwardly into the
spool bore 41.
Since compliant biasing is provided by the resilience of the ring 70, and
not by fluid pressure acting over chosen areas, it is not necessary to
construct the external face of the spool housing 10 and the bore 11 of
complementary stepped outline. The construction can therefore be
simplified.
The construction of FIG. 4 is otherwise the same as that of FIGS. 1 to 3
and corresponding reference numerals have been applied to corresponding
parts.
In the modified construction illustrated in FIG. 5, the "O" ring 70 is
replaced by a Belleville or spring washer 71 which again subjects the
spool housing 12 to a resilient biasing force in a similar manner to that
of, the "O" ring 70.
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